A rare pink diamond could set a new world record if it sells for its estimated price of £17-24 million at auction next week, Sotheby's said.

The 24.78-carat gem, described as "fancy intense pink", would top the previous record set by rival auctioneers Christie's when it sold the blue 35.56-carat Wittelsbach-Graff diamond for £15.2 million in 2008.

"This is undoubtedly one of the most important diamonds to appear at auction in recent years," David Bennett, the head of Sotheby's jewellery division, said in Geneva, Switzerland, where the auction will be held.

Potential buyers have already taken a strong interest, he said, adding: "It's been very, very well viewed."

But diamond experts said the Sotheby's price estimate is ambitious.

"The trade price is probably around 750,000 US dollars (£469,000) a carat," said Martin Rapaport, whose Diamonds.Net is a leading source on diamond trading and pricing. That would put the sales price at about £11.7 million, not including the auctioneer's commission and sales tax. A good price is a million a carat. I think only a consumer is going to pay that."

It is thought, however, that several factors could drive up the price.

First is the rarity and exceptional beauty of the stone, which has remained off the open market since it was sold 60 years ago by New York jeweller Harry Winston.

Economics, too, might play a role.

Global political and economic uncertainty is prompting the super-rich with significant disposable wealth to look for places to keep spare cash safe. In addition to gold, jewels and unique objects of art are considered attractive investments when currencies are sinking.